Condensed Consolidated Statement of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Balance at Apr. 30, 2021	$ 257,193	$ 24	$ 426,437	$ (167,836)	$ (1,432)
Balance, shares at Apr. 30, 2021		24,422,531
Issuance of common stock from equity incentive plans	608		608
Issuance of common stock from equity incentive plans, shares		14,984
Stock-based compensation expense	2,795		2,795
Net loss	(16,109)			(16,109)
Foreign currency translation (loss) gain	49				49
Unrealized holding (loss) gain from marketable securities	(129)				(129)
Reclassification adjustment for realized loss (gain) on marketable securities included in net loss	23				23
Balance at Jul. 31, 2021	244,430	$ 24	429,840	(183,945)	(1,489)
Balance, shares at Jul. 31, 2021		24,437,515
Balance at Apr. 30, 2022	185,093	$ 25	439,104	(250,175)	(3,861)
Balance, shares at Apr. 30, 2022		24,550,748
Issuance of common stock from equity incentive plans	168		168
Issuance of common stock from equity incentive plans, shares		20,124
Stock-based compensation expense	2,642		2,642
Net loss	(23,042)			(23,042)
Foreign currency translation (loss) gain	(403)				(403)
Unrealized holding (loss) gain from marketable securities	98				98
Reclassification adjustment for realized loss (gain) on marketable securities included in net loss	16				16
Balance at Jul. 31, 2022	$ 164,572	$ 25	$ 441,914	$ (273,217)	$ (4,150)
Balance, shares at Jul. 31, 2022		24,570,872